Apparatus for determining the amount of heat in the air



11,400,313, Patented Dc. 13, 1921.

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UNITED STATES PATENT OFFICE.

cm HEINRICH mom, or RHEYDT, GERMANY.

APPARATUS FOR DETERMINING THE AMOUNT OF HEAT IN THE AIR.

Specification of Letters Patent.

Patented Dec. 13, 1921.

Application filed February 20, 1914. Serial No. 819,958.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L,1313.)

To aZZ whom it may concern:

Be it known that I, CARL HEINRICH Pnorr, a subject of the GermanEmperor, residing at Rheydt, in Rhenish Prussia, Prussia, Germany, haveinvented certain new and useful improvements in Apparatus forDetermining the Amount of Heat in the Air, of which the following is aspecification.

Hitherto the determination of the amount of heat contained in the airnecessitated a very troublesome calculation, impossible to the generalpublic, and involved also several accurate measurements.

In order to ascertain the total heat, which is composed of the so-calledsensible heat or free heat of the air together with the latent heat ofthe water vapor contained in it, the usual procedure has hitherto beenfirst, to determine the relative or percentage amount of moisture in theair at the given temperature by means of a hygrometer, then to look upin a table the amount of moisture necessary to saturate the air at thegiven temperature, and then from this figure to calculate the absoluteamount of moisture con tained in a cubic meter of air in grams of water.After this the heat units could only be determined by furthercalculation, since for every cubic meter of air, the sensible heat mustbe reckoned with 0.306 calories per degree of temperature and inaddition the latent heat with 05948-06139 calories, according as thetemperature varies from 04LO C. for every gram of water vapor.

In order now to be able to follow the rise or fall of total heat fromtime to time, it was always necessary to make such laboriouscalculations over again, or to make use of tables containing millions offigures, from which one could only partly find out the values inquestion.

Both methods are so troublesome and take up so much time, that one wasgenerally satisfied in determining only the temperature from the drybulb thermometer, without re garding the actual heat, so that a falseimpression of the real amount of existing heat was obtained, and thebody experienced a different sensation of warmth, without having adirectly readable measurement for it.

he present invention relates to a new instrument which, in contradictionto the aforementioned troublesome and time-taking methods determines thetotal heat contained in a cubic meter or kilogram of air directly by asingle reading.

This new instrument consists, according to the invention, in a wet bulbthermometer the scale of which, in addition to or instead of the usualscale of thermometric de recs is graduated in heat units (calories).buch a scale may be arranged either on the thermometer itself orseparated from it and may be either fixed or revoluble (for recordinginstruments) The fact that, by means of such a scale the actual totalheat can at once be read off on a wet bulb thermometer seems at firstastonishing, since the total heat is made up of the heat of the dry air(sensible heat) together with the heat of the water vapor contained inthe air (latent heat) and of these the sensible heat only corresponds tothe temperature of the dry bulb thermometer, so that the omission of thedry bulb thermometer appears to be inadmissible.

That the invention is however practicable, and the manner in which thedesired scale of heat units for the wet bulb thermometer may be obtainedwith suflicient accuracy for many cases, will be apparent from thefollowing considerations.

Hitherto it has already been possible to calculate the total heat of theair from simultaneous observations of the dry and wet bulb thermometersand assuming a normal height of barometer, from the followingapproximate formula.

(Total heat) (calories):

. 0.306t+O.603 (f 0.64t(t-t different thermometers, looking up thecorresponding values of 7", in a table and a calculation according tothe formula given above. This method on account of its clumsiness is notusual in practice, but it is useful in the present instance in order tomake clear the essence of the invention.

' as a constant.

By multiplication and addition the above equation may be reduced to thefollowing form V Total heat, calories:

r 0.386t,+0.6O3f -0.O8t.

The first and second terms of the righthand side of this last equationare both functions of 25,, 2'. 6. they depend only on the temperature ofthe wet bulb thermometer, while the last term 0.08t may be regardedsolely as a correcting term and on account of its proportionately smallvalue may be entirely neglected, or better still, when measurements, notfar from the temperature of the room are in question can be considered 1The equation is then obtained in the form:

Calories:F,(t,)+F (2f )+C.(F and F being function of 25 and from this,by inserting the different values for m the scale of total heat for thewet bulb thermometer may be calculated.

In this way fairly accurate values are obtained, and any inaccuraciesare solely due to the formula employed above which is only anapproximate formula,rwl ile an absolutely exact scale may bemanufactured by using other calculations which are how ever even moretroublesome.

. The accompanying drawing shows in front elevation a wet-bulbthermometer, adapted as a calorimeter in accordance with the invention,7

a is a simple thermometer which is adapted as a so-called wet bulbthermom- 7 eter in the usual manner 6. g. by having an opaque groundglass bulbc at the lower end or by covering it with damp cloth. Thethermometer a in consequence of the evaporation taking'place around thebulb always shows a lower temperature than that of the surrounding air.On the right-hand side the scale I), which is graduated in degrees oftemperature is fitted, on the left hand side on the contrar a scale 0graduated in units of heat in accordance with this inven tion is fitted.This scale is determined in the above described or in other suitablemanner, and from it can be read off immediately the total heat containedin the air. The new instrument may therefore, if desired be used with adry bulb as an ordinary thermometer, or by wetting the ground glass bulbas a wet bulb thermom mm. HEINRELH PROTT. u. s] I Witnesses HELEN NUFER,ALBERT Norma.

